Field of the Invention
This invention relates to improved tethering for a transcatheter mitral valve replacement.
Background of the Invention
Valvular heart disease and specifically aortic and mitral valve disease is a significant health issue in the US. Recent advances have provided for the transcatheter deployment of a prosthetic cardiac valve. Compared to traditional valve replacement surgery which used an “open heart” surgical procedure and typically carries a 1-4% mortality risk in otherwise healthy persons, transcatheter deployment significantly reduces morbidity as well as reducing the cost of valve replacement therapy.
While replacement of the aortic valve in a transcatheter manner has been the subject of intense investigation, lesser attention has been focused on the mitral valve. This is in part reflective of the greater level of complexity associated to the native mitral valve apparatus and thus a greater level of difficulty with regards to inserting and anchoring the replacement prosthesis.
Several designs for catheter-deployed (transcatheter) aortic valve replacement are under various stages of development. The Edwards SAPIEN transcatheter heart valve is currently undergoing clinical trial in patients with calcific aortic valve disease who are considered high-risk for conventional open-heart valve surgery. This valve is deployable via a retrograde transarterial (transfemoral) approach or an antegrade transapical (transventricular) approach. A key aspect of the Edwards SAPIEN and other transcatheter aortic valve replacement designs is their dependence on lateral fixation (e.g. tines) that engages the valve tissues as the primary anchoring mechanism. Such a design basically relies on circumferential friction around the valve housing or stent to prevent dislodgement during the cardiac cycle. This anchoring mechanism is facilitated by, and may somewhat depend on, a calcified aortic valve annulus. This design also requires that the valve housing or stent have a certain degree of rigidity.
At least one transcatheter mitral valve design is currently in development. The Endo-valve uses a folding tripod-like design that delivers a tri-leaflet bioprosthetic valve. It is designed to be deployed from a minimally invasive transatrial approach, and could eventually be adapted to a transvenous atrial septotomy delivery. This design uses “proprietary gripping features” designed to engage the valve annulus and leaflets tissues. Thus the anchoring mechanism of this device is essentially equivalent to that used by transcatheter aortic valve replacement designs.
However, such designs still pose many unsolved problems such as heart remodelling, perivalvular leaking, inability to avoid fatigue failures, clotting, tissue damage, and so on. Accordingly, improvements are needed to address these and related problems in the art.